Adherence to Adjuvant Endocrine Therapy among Women Diagnosed with Early Breast Cancer

Estrogen receptor-positive (ER+) breast cancer is diagnosed in two-thirds of breast cancer cases in the US. Treatment with adjuvant endocrine therapy (AET) is recommended for five years for women with ER+ breast cancer. Despite the effectiveness of AET to improve survival and decrease cancer recurrence, adherence to recommended treatment is suboptimal. Understanding the factors that are associated with adherence to AET could improve overall breast cancer survival. Therefore, the goal of this dissertation is to identify target areas that are amenable for interventions in order to improve adherence to AET. The objective is threefold: 1) determine the association between combined out-of-pocket costs for AET medication and adherence; 2) examine how factors affect adherence to AET medication among women with very low adherence, moderately low adherence, and high adherence; and 3) understand, from the patient's perspective, how their physicians communicate with them about AET treatment. For objective 1 and 2 we conducted a retrospective cohort study using longitudinal medical and pharmacy claims data from the MarketScan Database from 2007-2011. We included women who were recently diagnosed and surgically treated for breast cancer and who filled at least one prescription for AET. For objective 3, we conducted semi structured in-depth interviews with breast cancer survivors taking AET. We found that high out-of-pocket costs for AET medication put patients at an increased risk of non-adherence. Factors associated with adherence to AET differed across the distribution of adherence and the use of mail-order pharmacies had the greatest influence on adherence. Physician-patient communication played an important role in both the initiation and management of AET. We found that women continue to take AET medication because their physician communicated key aspects of AET treatment in a way that they understood. Women also trusted and had confidence in their physicians. In summary, organizational-level interventions have the potential to improve adherence to AET. The use of mail-order pharmacies as well as lowering out-of-pocket costs may have the greatest influence on improving adherence. Women may also be more likely to continue AET treatment if physicians communicate the benefits of AET and actively engage patients in follow-up care to manage potential side effects.